lab size :)

Question
hi :) I have a 17kg 53cm tall lab that's 7months old, she's very slim with a long tail/body/head
I saw the parents yesterday and they don't look slim ,the mums  stocky like a show lab and the dad looks mostly lab but a little bit mixed. is it possible that my lab is a mix?or she's just a field Labrador? she was sold for $900 as a purebred but we got her for free off the people who bought her.
she was desexed at 6 months old, would this stunt her growth?
thanks :)

Answer
Many breeders don't realize that given a chance, females will breed with another male.  Some or all of a litter may be sired by the second mate.  So it could be the father is unknown.  It is also possible she takes after a dog further back in the line.  

There is some controversy about spaying females at 6 months.  Some people say they will end up taller, but more slender.  I can't see it making much difference in only a month.  The differences are hardly enough to be worth it to most dog owners to put up with the mess, hassles, and risks of having a female go through a season.  

All Lab puppies start out with the classic big, square heads.  Many of them lose the classic look by 6 months.  After a year old, the body becomes more barrel shaped and a less deep chest.  If their food isn't limited, they will become fat.  I don't think the head shape changes much.  

There are too many variables for me to give any definite answers.  There is DNA, but I am not sure about the reliability of popular tests such as http://www.biopetvetlab.com/dnahome.htm   http://www.wisdompanel.com/